1. Field of the Invention
This invention relates generally to system transfer switches and, more particularly, to manually-operated electrical transfer switches.
2. Background of the Invention
Continuous, uninterrupted electrical power is often needed for the proper operation of electrically-powered equipment. This is especially true where the electrically-powered equipment, such as water pumps, fans, elevators, refrigeration and cooling systems (among others), is being used for a critical application. For instance, electrically-driven water pumps may need electrical power to supply water for fire fighting, cooling, sanitary use, or production processes. Refrigeration and cooling systems may need electrical power to maintain a temperature-controlled environment in order to operate temperature-sensitive equipment, keep food from spoiling, or even keep blood banks at a proper temperature. Similarly, elevators rely on electrical power to insure personal safety and provide proper operation during emergency situations.
Unfortunately, due to adverse weather conditions and/or other conditions, power failures may often occur. In the event of a power failure, an electrical load that is connected to a first power source (e.g., a utility power source) may need to be quickly transferred to another, alternate power source (e.g., a generator) to keep the load functional. For this purpose, the power industry has adopted the use of so-called “electrical transfer switches” that are often key components of emergency and standby systems. An electrical transfer switch is generally a device that transfers an electrical load from a “normal” power source to an “emergency” power source. During a load transfer from power source to another power source, electrical contacts of the switch are sequentially opened and closed to couple the load to a desired power source. In an open configuration, for example, the switch contacts may be positioned to disconnect the load from all power sources. In a closed configuration, the switch contacts may be positioned to connect the load to a given power source. For example, in a first closed configuration, the switch contacts may be positioned to connect the load to a normal power source. In a second closed configuration, the switch contacts may be positioned to connect the load to an emergency power source.
To control opening and closing of switch contacts, an electrical transfer switch will typically include an apparatus that is used to place the electrical transfer switch in a desired configuration. In one example, this apparatus may be automatically-actuated (e.g. electrically-actuated during a power failure). In another example, the apparatus may be manually-actuated, allowing a switch operator to manually toggle switch contacts so as to transfer an electrical load from one power source to another power source. In the case of a manually-operated electrical transfer switch, it is thus desirable to provide a manually-actuated apparatus that can efficiently transfer an electrical load from a one power source to another in order to prevent damage that may result from the load being without power.
Further, some electrical transfer switches come equipped with two separate sets of electrical contacts that each individually control a connection to a given power source. In this type of switch, one set of electrical contacts may be dedicated to selectively connecting the load to a first power source (e.g., a “normal” power source). Another set of electrical contacts may be then dedicated to making or breaking a connection with a second power source (e.g., an “emergency” power source). For instance, a so-called “dual-shaft” electrical transfer switch may have two separate moveable contact assemblies, typically in the form of two moveable shaft assemblies carrying a respective set of electrical contacts that can be open or closed as needed.
Certain manually-actuated mechanisms may only be capable of opening and closing a single set of switch contacts at a time. As a result, for the purpose of positioning a dual-shaft transfer switch for instance, a user may subsequently have to operate two separate mechanisms that each individually control a single set of switch contacts. Thus, a common manually-actuated apparatus capable of opening/closing two separate sets of contacts is needed for use with an electrical transfer switch, such as a dual-shaft electrical transfer switch.
In addition, unlike electrically-actuated switching mechanisms, current manually-actuated mechanisms having complex designs generally perform switching between sources in a manner that could create substantial periods where the load is disconnected from a power source. This detrimental behavior may result in part from the inability of a human user to quickly and accurately engage the switching mechanism so as to avoid delays in opening and closing electrical contact assemblies. Thus, it would be beneficial to provide a less complex manually-actuated mechanism that is capable of switching at an equivalent to that of an electrically actuated apparatus.